Fix the static_functions_not_mutating error messsage

[felixinkinto]

Fix #77835

[xedin]

Thank you for the contribution! I left a comment inline about the text and as a separate note: please modify existing tests (because the text is now different) or make sure that we have tests for both nonmutating and mutating attributes that exercise the new diagnostics before we can run CI and land this.

[xedin]

Instead of clamping mutating and nonmutating together it would be better to print one or the other depending on what the attribute was, a boolean flag could be used to distinguish between the two (i.e. no_overloads_match_exactly_in_call does a similar thing reference vs. call).

Instead of "operate" we can use "cannot access" and the "because" part can be turned into a note.

[felixinkinto]

@xedin
Thanks for the advice!
I fixed based on your suggestion.

[xedin]

I left one more small note inline. We also have a few tests that use the diagnostic and they'd need to be adjusted before we can land this:

test/Sema/immutability.swift:134
test/decl/subscript/static.swift:23
test/decl/subscript/static.swift:24
test/decl/overload.swift:413

[AnthonyLatsis]

@felixinkinto Next time, please ask us to assign you to an issue before you start working on one. A good first issue is a queue, not a race. We want to avoid instances of multiple people independently working on them.

[felixinkinto]

@xedin sorry for the delay for long. I addressed the feedback. May I ask some questions to do behaviour checks?

1. Does the order matter? I realized note usually follows the error in other areas.

➜  test xcrun -sdk macosx build/Ninja-RelWithDebInfoAssert/swift-macosx-arm64/bin/swiftc test.swift
test.swift:4:3: error: 'nonmutating' modifier cannot be used on static functions
2 |
3 | struct S {
4 |   nonmutating static func foo() {}
  |   |                       `- note: static members cannot access instance properties or self
  |   `- error: 'nonmutating' modifier cannot be used on static functions
5 |
6 |

2. After testing the locally built compiler in Xcode according to this manual, it seems that the existing swiftc is overriding the errors in the IDE.
   this build log shows my local compiler.

this is still the default swiftc

[felixinkinto]

@felixinkinto Next time, please ask us to assign you to an issue before you start working on one. A good first issue is a queue, not a race. We want to avoid instances of multiple people independently working on them.

@AnthonyLatsis
sorry I’ll make sure to ask for an assignment before starting work on an issue next time.

[felixinkinto]

@swift-ci please test Windows platform